1. Field of the Invention
The invention relates to a symmetric mixer usable for millimeter wave frequency changing and an ultra high frequency radio-electric receiver using such a mixer.
2. Description of the Prior Art
For ultra-high frequencies, a symmetric mixer comprises two detector diodes, for example two Schottky diodes, each receiving at the same time the signal to be treated and the frequency of a local oscillator. The output signals of the two diodes, at the so-called intermediate frequency of the receiver, are added together, whereas the amplitude variations (amplitude noise coming from irregularities of the local oscillator) are subtracted, which allows for compensation of this defect.
In the construction of such a mixer, there are difficulties because, frequently, for millimeter waves, the signal to be processed and the local signal arrive through two separate wave-guides. In order to favor the signal to be processed, which often comes from an extremely small electro-magnetic field, the diodes are mounted directly in the wave-guide which conveys the signal to be treated. Several problems are then posed and in particular:
the coupling of the two wave-guides by means of a common member; PA1 the coupling of the diodes with the electric fields of the two signals to be mixed; PA1 the arrangement of the biasing inputs of the diodes and of the intermediate frequency signal outputs.
The invention enables these problems to be resolved in the form of solutions advantageous from the industrial point of view.